The present invention relates to the field of electronic devices, and, more particularly, to electronic devices including micro-fluidic cooling of one or more integrated circuits and associated methods.
Integrated circuits are widely used in many types of electronic equipment. An integrated circuit may include a silicon or gallium arsenide substrate including a number of active devices, such as transistors, etc. formed in an upper surface of the substrate. It is also typically required to support one or more such integrated circuits in a package that provides protection and permits external electrical connection.
As the density of active devices on typical integrated circuits has increased, dissipation of the heat generated has become increasingly more important. In particular, a relatively large amount of heat may be generated in multi-chip modules (MCMs), microwave transmitters, and photonic devices, for example. U.S. Pat. No. 5,987,893 to Schulz-Harder et al. discloses a cooling package, such as for a laser device, including channels through which cooling water flows. Heat is removed using a series of Peltier elements in
Advances in micro-electromechanical (MEMs) technology have allowed designers to develop further cooling techniques for integrated circuits based on circulating dielectric cooling fluids adjacent an integrated circuit to thereby remove waste heat. For example, U.S. Pat. No. 5,876,187 to Afromowitz et al. discloses micro-pumps with associated valves that may be used for a number of applications, such as environmental, biomedical, medical, biotechnical, printing, analytical instrumentation, and miniature cooling applications.
Heat may be removed from an integrated circuit by free convective cooling of gases or liquids. The liquids typically remove more heat. Forced convective cooling may provide additional efficiency as the gases or liquids are circulated in contact with the device to be cooled. Cooling using boiling liquid provides yet higher efficiency.
Unfortunately, an integrated circuit may operate at different power levels and thereby generate different amounts of waste heat. Accordingly, a typical MEMs micro-cooling system may not operate efficiently over all of the possible operating ranges of the integrated circuit.
In view of the foregoing background it is therefore an object of the invention to provide an electronic device and associated methods which provide highly efficient cooling for the one or more integrated circuits in the overall package.
This and other objects, features and advantages in accordance with one aspect of the present invention are provided by an electronic device comprising a package surrounding at least one integrated circuit, a micro-fluidic cooler in the package, and a controller for controlling the micro-fluidic cooler so that the cooling fluid provides evaporative cooling. The controller may also be provided in the package. Evaporative cooling provides very efficient cooling since it may be based upon droplet impingement and boiling of the cooling fluid. Such evaporative micro-cooling is considerably more efficient than free convective or forced convective cooling. The electronic device may be relatively compact and yet have a highly efficient cooling system for the removal of waste heat from the at least one integrated circuit.
The electronic device may comprise a power consumption sensor connected to the at least one integrated circuit, and the controller may control the micro-fluidic cooler responsive to the power consumption sensor. Alternately or additionally, a temperature sensor may be connected to the at least one integrated circuit, and the controller may control the micro-fluidic cooler responsive to the sensed temperature.
The micro-fluidic cooler may comprise at least one droplet generator for generating and impinging droplets of cooling fluid onto the integrated circuit. More particularly, the at least one droplet generator may comprise at least one micro-electromechanical (MEMs) pump.
The electronic device may also include at least one heat exchanger carried by the package and connected in fluid communication with the micro-fluidic cooler. In one particularly advantageous class of embodiments, the package may have a parallelepiped shape with a first pair of opposing major surfaces, a second pair of opposing side surfaces and a third pair of opposing end surfaces. In these embodiments, the at least one heat exchanger may preferably comprise a pair of heat exchangers, each coupled to a respective one of the second pair of opposing side surfaces. This configuration may facilitate stacking of a plurality of such units or modules. Each module may also comprise electrical connectors carried by at least one of the first pair of opposing major surfaces and the third pair of opposing end surfaces.
The package may comprise a base and a lid connected thereto defining a cavity receiving the at least one integrated circuit. The micro-fluidic cooler may comprise at least one micro-fluidic passageway extending through the base and directed toward the at least one integrated circuit. In addition, the at least one integrated circuit may comprise an active surface comprising active devices therein, and the at least one integrated circuit may be positioned so that the active surface is adjacent the at least one micro-fluidic passageway. In this arrangement, the droplets of the cooling fluid may be delivered directly onto the active surface of the integrated circuit to efficiently remove heat therefrom. Also, using such flip chip bonding, a plurality of bodies, such as solder balls, may connect the at least one integrated circuit to the base in spaced apart relation therefrom so that cooling fluid also flows adjacent the bodies and into the cavity. Heat is also removed from the solder balls, and cooling efficiency is further enhanced.
The package may comprise low temperature co-fired ceramic (LTCC) material. This material offers advantages in terms of ruggedness, and an ability to form recesses and passageways therein.
Another aspect of the invention relates to a method for cooling at least one integrated circuit in a package also including a micro-fluidic cooler therein. The micro-fluidic cooler may also include a cooling fluid. The method preferably comprises controlling the micro-fluidic cooler so that the cooling fluid provides evaporative cooling. The controlling may further comprise sensing power consumption of the at least one integrated circuit and controlling the micro-fluidic cooler responsive thereto. Controlling may alternately comprise sensing a temperature of the at least one integrated circuit and controlling the micro-fluidic cooler responsive thereto.